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Reproductive function is intimately related to caloric consumption. During fasting states, the hormones regulating reproduction, those of the hypothalamic-pituitary-gonadal axis, in particular, are severely altered. With the exciting observations that the obese (ob) gene product leptin, may also modulate neuroendocrine functions, we examined leptin's ability to prevent the consequences of fasting on reproductive hormones. Two groups of male rats, aged 65 days old, were either fasted and saline-injected or fasted and leptin-treated for approximately three days. Another group was given free access to rat chow. Leptin was able to prevent the fasting-induced fall of serum testosterone. Similar to testosterones dependence on leptin, leptin concentrations were somewhat dependent on testosterone. Castration accelerated the normal, age-related increase in serum leptin. Leptin also prevented the fasting-induced fall in luteinizing hormone (LH). The increase of beta-LH mRNA seen in the fasting state was prevented by leptin. There were no differences noted in luteinizing hormone releasing hormone (LHRH) mRNA among any of the groups. While neither fasting nor fasting plus leptin caused changes in serum prolactin, the increase in prolactin mRNA seen in fasted animals was prevented by leptin treatment. These data support the hypothesis that leptin plays a specific role in mediating the response of reproductive hormones to the nutritional status of the organism.

Background: Ethanol exposure impairs mammalian reproductive function. However, the mechanisms are not fully understood., Methods: Adult female rats were given an ethanol or a calorically matched control diet. A third group was given a liquid nonethanol diet. Half the animals were killed at 2 weeks (short chronic) and the other half at 2 months (long chronic), all on the day of proestrous on the basis of daily vaginal smears., Results: The major effect of ethanol feeding was disruption in the estrous cycle. Although all of the pair-fed animals continued to cycle, 40% of the ethanol rats in the short chronic study had disruption of their cycles. In the long chronic study, 83% of the ethanol animals had abnormal cycling, in contrast to 16% of the pair-fed controls. The nature of the cycle disruption was prolongation of diestrous, with an increased time interval between proestrous surges. In four ethanol-fed rats, there was complete cessation of the estrous cycle. However, ethanol did not decrease ovarian or uterine weight. Ethanol significantly increased serum estradiol in the short chronic but not long chronic study, whereas progesterone was unchanged. Ethanol did cause a significant reduction in circulating insulin-like growth factor., Conclusions: The major effect of both short chronic and long chronic ethanol exposure was disruption of the estrous regularity, leading to a decreased number of proestrous surges. Part of the mechanism of this disruption might be a transient estrogen increase or a decrease in circulating insulin-like growth factor.

Teenage drinking continues to be a major problem in the United States as well as abroad. A significant depression in serum testosterone in adolescents who consume EtOH has been well described. In the male rodent model, a similar fall in testosterone has been reported, and prevention with the opiate blocker naltrexone has been demonstrated. To explore further the impact of chronic EtOH exposure on the reproductive axis in peripubertal rats, we designed this study specifically to define whether or not there was recovery after abstinence by examining reproductive hormones and their genes during and after EtOH exposure. Peripubertal male rats 35 d old were fed an EtOH-containing diet or a calorically matched control diet for 60 d. A third group was fed the control liquid diet ab libitum. EtOH was then withdrawn and all animals were fed standard rat chow and water ad libitum for an additional 3 mo. The EtOH-imbibing animals were found consistently to weigh less than their pair-fed mates and liquid diet ad libitum animals. Serum testosterone levels and testicular weights were significantly decreased by EtOH whereas serum estradiol levels were higher, suggesting enhanced peripheral conversion by EtOH. Spermatogenesis, assessed by histological parameters, was unaltered by EtOH. Serum luteinizing hormone levels were not different among the groups. Hypothalamic luteinizing hormone-releasing hormone mRNA levels were unaffected by EtOH. During the 3-mo recovery period, all the changes reversed, with a significant increase noted in testosterone. All other parameters remained the same among the groups. Thus, although chronic EtOH exposure in the peripubertal age period results in significant reproductive alterations, there is complete recovery on withdrawal.

The effects of ethanol (EtOH) and nitric oxide (NO) are well known in the adult male rat reproductive axis. In the present study, we investigate the effects of EtOH, NO, and their interaction on key genes and reproductive hormone levels in mid- (45-day) and late pubertal (55-day) male rats. Using three different NO synthase blockers--N'omega-nitro-L-arginine methyl ester (L-NAME), N'omega-nitro-L-arginine (L-NA), and 7-nitroindazole--we show that it is possible to block, in part, some of the disruptive effects of EtOH. L-NAME totally prevented the EtOH-induced fall in serum testosterone in both 45- and 55-day-old rats (p < 0.05 and p < 0.001, respectively). On the other hand, the D-NAME, an inactive isomer of L-NAME, did not protect testosterone from suppression caused by EtOH. Similarly, L-NA and 7-nitroindazole prevented the suppression of testosterone caused by EtOH in 55-day-old animals (p < 0.001 L-NA and p < 0.05 for 7-nitroindazole), but not in the 45-day-old rats. Serum luteinizing hormone (LH) was significantly reduced by EtOH in all the studies in both age groups. L-NAME (but not D-NAME) and L-NA prevented this inhibition in 55-day-old animals (p < 0.001 for L-NAME and p < 0.01 for L-NA). However, only L-NA was able to prevent the effects of EtOH on LH in the 45-day-old rats. 7-Nitroindazole was unable to prevent the decrease in LH in either age group. Despite changes in the other reproductive hormones, there were no consistent changes in hypothalamic concentrations of either LH releasing hormone (LHRH) or its precursor, pro-LHRH. No treatment caused any change in steady-state levels of beta-LH mRNA. There were no consistent changes in pro-LHRH mRNA; but, interestingly, in 45-day-old rats, L-NA given with or without EtOH lead to a significant fall in LHRH gene expression. Our findings indicate that the acute suppressive effects of EtOH on the hypothalamic-pituitary-gonadal axis of the pubertal male rat can be at least partially prevented by NO synthase blockade.

Teenage drinking continues to be a significant problem in the U.S., as well as abroad. We have previously demonstrated that opiate blockade with naltrexone, a drug currently used in patients to diminish alcohol craving, prevented the fall in serum testosterone seen after acute ethanol (EtOH) exposure in young, peripubertal male rats. To follow-up on this reversal, a series of experiments was performed to determine if naltrexone would also prevent the testosterone suppression caused by chronic EtOH exposure. Peripubertal rats either 45 days old (mid-pubertal) or 55 days old (late pubertal) were fed an EtOH-containing liquid diet or pair-fed control diet for 14 days. Each animal was implanted with either a naltrexone containing or placebo pellet before starting the liquid diet. In each age group, EtOH alone significantly suppressed testosterone, whereas naltrexone prevented this fall, although it had no effect alone. Serum luteinizing hormone was also suppressed by EtOH; however, naltrexone did not abrogate this fall. In the 45-day-old animals, beta-luteinizing hormone mRNA levels rose significantly in the EtOH group, but not when naltrexone was coadministered with EtOH. There was no change in hypothalamic luteinizing hormone releasing hormone (LHRH) mRNA, pro-LHRH, or LHRH in any group at either age. Thus, naltrexone is able to partially prevent the EtOH-induced suppression of gonadal testosterone of young, adolescent male rats. This effect appears to be mediated directly at gonadal level, because hypothalamic and pituitary hormone changes were minor and nonsignificant.

Proper nutritional status is critical for maintaining growth and metabolic function, playing an intimate role in neuroendocrine regulation. Leptin, the recently identified product of the obese gene, may very well be an integral signal which regulates neuroendocrine responses in times of food deprivation. The present study examines leptin's ability to regulate hormonal synthesis and secretion within the GRF-GH-IGF axis in the adult male rat during almost 3 days of fasting. Serum levels of GH and IGF-I were drastically suppressed by fasting. Daily leptin administration was able to fully prevent the fasting-induced fall in serum GH. Leptin failed to restore IGF-I to control levels, however, suggesting possible GH resistance. Fasting caused an insignificant increase in GH mRNA, while leptin injections significantly increased steady-state levels of this message. The GRF receptor (GRFr) message was not altered with fasting or leptin treatment. Leptin also exhibited effects at the hypothalamic level. Fasting induced a sharp fall in GRF mRNA expression and leptin injections partially prevented this fall. However, there were no observed changes in the hypothalamic GRF content. These results provide evidence that leptin may function as a neuromodulator of the GRF-GH-IGF axis communicating to this hormonal system the nutritional status of the animal.

Teenage drinking is a major problem in the United States, as well as abroad. Besides psychosocial implications, ethanol (EtOH) has detrimental effects on the reproductive system. Clinical problems associated with reduced reproductive hormones include osteoporosis, decreased muscle function, anemia, altered immune function, prostate involution, and decreased reproductive abilities. Education coupled with strategies aimed at preventing these deleterious consequences even in the face of continued EtOH intake is extremely important. We have tested the possibility that naltrexone, a drug currently used in patients to decrease alcohol craving, might also prevent the fall in the male hormone, testosterone, caused by EtOH exposure. Rats aged 35 days old (prepubertal), 45 days old (midpubertal), and 55 days old (late pubertal) were injected (intraperitoneally) with either saline, EtOH, naltrexone, or EtOH plus naltrexone. In the two older age groups, EtOH significantly suppressed testosterone, which was prevented by administration of naltrexone. In the youngest animals, there was no treatment effect presumably due to low basal levels of testosterone. EtOH similarly reduced luteinizing hormone (LH), but this suppression was not prevented by naltrexone. There was no consistent effect of any treatment on hypothalamic concentration of pro-LH releasing hormone (RH) (LHRH), LHRH, or on steady-state levels of LHRH mRNA. We conclude that, as animals progress through puberty, EtOH suppresses LH and testosterone. The testosterone decline can be prevented by opiate blockade with naltrexone, an effect primarily seen at gonadal level. Thus, naltrexone, a drug already used clinically to reduce EtOH intake, also has protective physiological effects on the endocrine system.

It is the purpose of this study to investigate the effects of acute ethanol (EtOH) on the female rat hypothalamic-pituitary-gonadal (HPG) axis. The molecular and cellular mechanistic details of such effects have been studied intensively in the male rat. However, there has been relatively little in-depth study of EtOH's effects on the adult, postpubertal female rat. Adult female rats with confirmed 4- or 5-day estrous cycles were given a single injection of EtOH or saline between noon and 1:00 PM on proestrous and were killed at 4:00 PM. EtOH caused a sharp 97% reduction in luteinizing hormone (LH) serum levels (p < 0.001), compared with controls with no concomitant change in LH mRNA. EtOH also significantly reduced hypothalamic LH releasing hormone (LHRH) by 49% (p < 0.01), with no change in content of the precursor pro-LHRH compared with saline-injected controls. The ratio of LHRH to pro-LHRH was also significantly reduced by EtOH (p < 0.05), compared with control. There was no EtOH-induced change in LHRH mRNA. Compared with saline, EtOH reduced both serum estradiol by 37% (p < 0.02) and progesterone by 47% (p < 0.001). These results show that EtOH has profound disruptive effects on the female HPG axis. Our data suggests that EtOH decreases the releasable LHRH pool either by decreasing conversion of pro-LHRH to LHRH and/or by increasing local LHRH degradation. This acutely restricts the release of LH and subsequent estradiol and progesterone secretion.

Alterations in the protein kinase C (PKC) pathway may interrupt anterior pituitary luteinizing hormone (LH) synthesis and/or secretion, which may impair normal reproductive function. Work by our laboratory and others has shown that EtOH has profound deleterious effects on the regulation of the hypothalamic-pituitary-gonadal (HPG) axis. The present study focuses on PKC translocation from the cytosol to the membrane of anterior pituitary after acute EtOH exposure. Serum levels of LH were measured at three time points (15, 30, and 90 min) after an IP injection of either saline or 3 g/kg EtOH in adult castrated male rats. LH levels dropped significantly (p < 0.03) in EtOH-injected compared to saline-injected control animals. In the same animals, EtOH significantly suppressed PKC localization at its active site at the pituitary cell membrane (p < 0.05). These findings suggest that the mechanism of EtOH's suppression of LH is mediated, at least in part, through a decrease in PKC translocation to the anterior pituitary cell membrane.

Jurkat cells were used to study the immunomodulatory role of luteinizing hormone-releasing hormone (LHRH) in immune cells. The Jurkat cell, a human mature leukemic cell line, phenotypically resembles resting human T lymphocytes and has been widely used to study T cell physiology. The data from this study demonstrate that the Jurkat cell concentration of immunoreactive LHRH was 210 +/- 36 pg/10(6) cells and that of proLHRH was 188 +/- 27 pg/10(6) cells (means +/- S.E.M.). The authenticity of this LHRH immunoreactivity is documented in two ways. First, both Jurkat LHRH and proLHRH immunoreactivity demonstrate dilutional parallelism with hypothalamic LHRH and proLHRH. Second, Jurkat lysates show LHRH bioactivity by releasing luteinizing hormone from rat anterior pituitary cells in culture. The presence of substantial amounts of LHRH in medium in which Jurkat cells were cultured for 72 h indicated that LHRH can be released from the cells. Using specific primers to exons 2 and 4 of the LHRH gene, we have found that Jurkat cells (like human T cells) express LHRH mRNA. The LHRH agonist, des-Gly10,D-Trp6-LHRH ethylamide, significantly increases the proliferative activity of Jurkat cells, as assessed by tritiated thymidine incorporation, from 15980 +/- 1491 c.p.m. in control to 28934 +/- 3395, 30457 +/- 3861 (P = 0.05 vs control) or 35299 +/- 5586 c.p.m. (P < 0.01 vs control) with 10(-11), 10(-9) or 10(-7) M agonist respectively. LHRH antagonist, [D-pGlu1,D-Phe2,D-Trp3,6]-LHRH, at a concentration of 10(-8) M decreases Jurkat cell proliferative activity form 17145 +/- 526 c.p.m. in control medium to 10653 +/- 1323 c.p.m. (P = 0.05). Co-incubation with the LHRH antagonist completely inhibits the proliferative stimulation induced by the LHRH agonist. Furthermore, applying monoclonal LHRH antibody to Jurkat cells inhibits the cell proliferative activity assessed by tritiated thymidine incorporation from 19900 +/- 2675 c.p.m. in control to 15680 +/- 2254, 15792 +/- 1854 and 9700 +/- 908 c.p.m. in media with 1:40, 1:20 and 1:10 dilution of purified antibody respectively (P < 0.01, 1:10 dilution compared with control). In addition, the cAMP level in LHRH-stimulated Jurkat cells is decreased to 74, 27 and 57% of control levels after 15, 30 and 45 min respectively of exposure to 10(-7) M LHRH agonist. In summary, Jurkat cells produce, process and release immunoreactive and bioactive LHRH, as do normal human T cells. Endogenous and exogenous LHRH increase Jurkat cell proliferative activity, and cAMP may be involved in LHRH-induced Jurkat cell proliferation. The Jurkat cell may be a useful model with which to study the role of LHRH in human T cell function.

Little is known about the neuroendocrine impact of cocaine as it relates to pituitary growth hormone secretion. In these studies, in adult male rats, intracerebroventricular administration of cocaine caused a potent dose-related suppression of circulating growth hormone (GH) in animals sacrificed 15 min after drug administration. We conclude that in the adult male rat cocaine suppresses plasma GH levels.

The impact of ethanol on the male reproductive axis are multiple and varied, with both gonadal and control hypothalamic-pituitary pertubations being reported. There appears to be a discrepancy, however, between the in vivo and in vitro effects of ethanol on hypothalamic luteinizing hormones releasing hormone (LHRH) and the pituitary gonadotropins luteinizing hormone (LH) and follicle stimulating hormone (FSH). While in vivo data suggests a decrease in LHRH release after EtOH, in vitro studies find no effect on secretion. Similarly, in vivo acute EtOH profoundly diminishes LH synthesis and secretion, while in vitro impaired release with no alteration in the transcription of beta LH has been found. A potential exploration for these discrept results could be the in vivo metabolism of EtOH into acetaldehyde and acetate, or the subsequent formation of salsolinol, a product of acetate combining with dopamine. To test this possibility, a series of in vitro experiments were conducted exposing dispensed anterior pituitary cells from male rats to different doses of acetaldehyde, acetate or salsolinol for varying amounts of time for which gonadotropin secretion and beta LH mRNA levels were assessed. The results demonstrated no effect of either acetaldehyde or acetate on basal or LHRH stimulated LH release, FSH release or steady-state beta LH mRNA levels. These data suggest that the metabolites of EtOH, which occur in vivo but not in vitro, are not responsible for the discrepant gonadotropin changes reported between the in vivo and in vitro setting. Other potential mechanisms to explain this phenomenon include differences in the molarity of EtOH, hyperprolactinemia and suprapituitary influences including hypothalamic LHRH, catecholamines, excitatory amino acids, substance P and beta endorphin.

Continuous administration of LHRH agonist suppresses the pituitary-gonadal axis, achieving chemical castration. Thus, LHRH agonist has been used as an alternative (to surgical castration) for the treatment of steroid-dependent prostate cancer. However, recent reports have demonstrated that LHRH agonist had a direct inhibiting effect on prostate cancer cell proliferation and that cancerous prostate tissue contained a LHRH-like peptide. In this paper we are reporting for the first time that the normal rat ventral prostate contained immunoactive and bioactive LHRH as well as its precursor molecule, pro-LHRH. Our investigation showed that the LHRH concentration in prostate increased 2 weeks after castration from 1.68 +/- 0.09 to 3 +/- 0.2 pg/mg tissue (P < 0.001). At the same time, the concentration of pro-LHRH decreased from 149 +/- 6.5 to 68 +/- 6.8 pg/mg tissue (P < 0.001). Furthermore, intact rat prostate expressed LHRH mRNA, which increased 13-fold 2 weeks after castration. In summary, the prostate of intact Sprague-Dawley rats has the capacity to produce the LHRH precursor and process it to the mature decapeptide, and this production/processing increases significantly after castration.

An immunomodulatory role for LHRH was suggested when we reported the presence of immunoactive and bioactive LHRH and its mRNA in rat splenic and thymic lymphocytes. In this paper we report that human peripheral T-cells as well as its subsets CD4+ and CD8+ contained immunoactive and bioactive LHRH. Furthermore, analysis of phytohemagglutinin (PHA)-activated T-cell lysates for LHRH by RIA demonstrated that the mean concentration of LHRH in PHA-activated T-cells increased from 45 +/- 4.5 to 64 +/- 7 pg/10(6) cells after 24 h of culture and from 47 +/- 3.6 to 117 +/- 11.8 pg/10(6) cells (P < 0.01) after 48 h. While the LHRH concentration in PHA-activated cells increased over the last 24 h of culture h from 64 +/- 7 to 117 +/- 11.8 pg/10(6) cells (P < 0.001), there was no change in mean concentration of LHRH in T-cells kept in medium alone. In a preliminary study we found that fresh T-cells contain 20 +/- 1.4 pg pro-LHRH/10(6) cells, and PHA stimulation increased the pro-LHRH content similar to the increase in LHRH. As with unfractionated T-cells, a significant PHA-induced time-dependent enhancement of intracellular LHRH was noted in CD4+ and CD8+ T-cells. RNA extracted from lymphocytes was subjected to reverse transcription-polymerase chain reaction analysis using LHRH and histone-3.3, primers, the latter as an internal control. The polymerase chain reaction-generated data demonstrated that the relative amount of LHRH mRNA in cultured, but non-PHA-stimulated (resting), cells diminished dramatically between 5-24 h, but recovered by 48 h of culture. The relative amount of LHRH mRNA in PHA-stimulated cells revealed a markedly different pattern. LHRH message expression in PHA-activated cells increased slightly at 5 h of culture and was maximally stimulated by 24 h, but declined by 48 h of culture. The PHA activation-induced time-dependent enhancement of intracellular accumulation of LHRH peptide at 5 and 24 h was accompanied by increased LHRH message. However, the increased concentration of LHRH peptide at 48 h coincided with decreased LHRH message expression. The data from total protein synthesis in PHA-activated cells showed a progressive increase in protein synthesis, a pattern entirely similar to the changes in the cell content of LHRH.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of ethanol (EtOH) on GH and PRL have been previously explored, and a dicotomy in results noted. While serum GH levels appear to fall after EtOH exposure, PRL levels rise. We have attempted to expand these studies by examining the impact of acute or "binge" EtOH in vivo on GH and PRL synthesis and secretion. At 0.5, 1.5, and 3.0 h after one dose of ip EtOH, serum GH levels fell significantly compared with those seen in saline-injected controls. This correlated with a fall in GH mRNA levels, but no change in pituitary GH content. Conversely, serum PRL levels rose significantly, while the mRNA for PRL decreased by approximately 20%. There was no change in pituitary PRL content. Interestingly, the mRNA for pit-1 (GHF-1), a transcription factor important to both GH and PRL gene expression, was unchanged at any time point. Despite the fall in GH and PRL mRNA levels, the pituitary cAMP content was markedly elevated at 0.5 h, with no change at any other time point. In summary, acute EtOH exposure in vivo appears to dampen both GH and PRL synthesis, while serum levels behave dissimilarily. Possible explanations for these findings are discussed.

Previous works from our laboratory and others have shown that there is a PRL-like immunoreactive protein with immunological, chromatographic, and biological characteristics identical to those of pituitary PRL, and this is widely distributed in the rat central nervous system. Since pituitary PRL is important in controlling hypothalamic LHRH release, we have hypothesized that hypothalamic PRL-like immunoreactive protein might serve a similar role, that of an endogenous neuromodulator influencing hypothalamic LHRH release. To this end, we have examined the effect of PRL antiserum and normal rabbit serum on the release of immunoreactive LHRH from rat hypothalamic fragments cultured in vitro. In the first experiment, LHRH release from hypothalami of intact rats, bathed in PRL antiserum (1:200 in Krebs-Ringer bicarbonate buffer), was significantly lower than that from hypothalami bathed in normal rabbit serum (1:200 in Krebs-Ringer bicarbonate buffer) for 90 min of incubation. It was, however, possible that the PRL, immunoneutralized in the first experiment, was material that represented contamination from pituitary PRL. Therefore, we repeated the experiment using hypothalami from animals that had been hypophysectomized 2 weeks before death. Again, PRL antibody significantly inhibited the release of LHRH compared with that by hypothalami incubated in normal rabbit serum. Since testosterone is important to LHRH synthesis, a third experiment was carried out using hypothalami from hypophysectomized male rats that had been implanted sc with testosterone-containing capsules 72 h before death. By 72 h serum testosterone levels had normalized. PRL antibody added to medium containing hypothalamic explants from these animals substantially inhibited in vitro LHRH release, a pattern essentially similar to that seen in intact and hypophysectomized animals without testosterone replacement. From these studies we have concluded that hypothalamic PRL is an important neuromodulator that promotes the release of LHRH from the hypothalamus. Testosterone, at least under the experimental conditions employed, appears not to be essential in this hypothalamic PRL-LHRH interaction.

An interaction between the immune and endocrine systems has been long known. This association is further strengthened by the finding that splenic lymphocytes have the capacity to produce molecules similar to if not the same as classical hormones, including several members of the opiate family, PRL, GH, and neuropeptide Y. Because of such findings and because of information from other laboratories suggesting that LHRH might have direct effects upon the immune system, we hypothesized that immune cells themselves might contain LHRH. Lymphocytes were purified from spleens of intact adult male Sprague-Dawley rats and the cells were lysed with sodium hydroxide. The concentration of immunoreactive LHRH was 403 +/- 184 pg/20 X 10(6) lymphocytes. Increasing amounts of lymphocyte lysate displaced [125-I]LHRH from LHRH antibody in a manner parallel to that produced by synthetic hypothalamic LHRH, suggesting immunologic similarity between lymphocyte and hypothalamic LHRH. Lymphocyte LHRH-like immunoactivity coeluted from Nova-Pak C18 columns with synthetic hypothalamic LHRH. When lymphocyte lysates were applied to rat anterior pituitary cells in monolayer culture, significant stimulation of LHRH secretion was seen, from 2,144 +/- 54 pg LH/ml.4 h to 15,364 +/- 587 pg LH/ml.4 h (P less than 0.001), a finding verified in five additional experiments. In other studies, this LH response evoked by lymphocyte lysates was found to be dose dependent and could be significantly inhibited by an LHRH-antagonist. Furthermore, when lymphocyte lysate and identically treated synthetic LHRH were HPLC fractionated, there was coelution of lysate and hypothalamic LHRH bioactivity. The lysate itself contained no substantial LH immunoreactivity. Thus, lymphocytes from spleens of adult male rats contain an immunoactive and bioactive LHRH, a finding further strengthening an association between the endocrine and immune systems.

A variety of indirect data suggest that the luteinizing hormone (LH) lowering effects of ethanol (ETOH) are mediated at a hypothalamic level decreasing the synthesis and/or release of LH-releasing hormone (LHRH). Little direct data support this concept, however. The current study was, therefore, designed utilizing a perifusion system with frequent sampling for LHRH with and without ethanol added to determine if ethanol had a direct effect on basal or stimulated LHRH release. A variety of secretagogues, including dopamine, norepinephrine, naloxone, prostaglandin E2, and a high dose of potassium were utilized. Ethanol at a dose of 300 mg% did not alter either basal or secretagogue-stimulated LHRH release from the hypothalami of ethanol-naive male rats. Thus, ethanol did not appear to have a direct effect on LHRH in this system. Alterations in LHRH release by ethanol may occur at a suprahypothalamic level, involving neurotransmitter-LHRH interactions. Alternatively, the well-described lowering effect of ethanol on LH may be secondary to a direct pituitary locus of action, or involve a metabolic breakdown product of ethanol rather than ethanol itself.

We have previously described the presence and wide distribution of a luteinizing hormone (LH)-like peptide, widely distributed in the rat central nervous system, with highest levels in the hypothalamus. We have found that intracerebroventricular injection of 100 micrograms colchicine causes a significant rise in hypothalamic LH, from 549 +/- 170 pg/mg protein (n = 12) in controls to 1,679 +/- 279 pg/mg protein (n = 13) in treated animals, p less than 0.01. There was no associated change in levels of LH in the pituitary. Since colchicine stops axoplasmic flow, these findings of colchicine-induced increase in hypothalamic LH indicate that at least a portion of hypothalamic LH is present in long-axoned neuronal elements with cell bodies within the hypothalamus and axons extending to the extrahypothalamic brain. Thus, hypothalamic LH does not solely represent measurement of LH in cells of the contignous pars tuberalis.

Our laboratory has previously described the widespread distribution of an immunoreactive and bioactive rat growth hormone (rGH)-like protein in rat brain. It has also been demonstrated that regulation of pituitary rGH secretion is at least partly mediated by a short-loop negative feedback system. In such a system, increased levels of rGH, acting at a suprapituitary locus, would decrease pituitary GH secretion. Thus, the present study has dealt with attempts to further investigate the hypothesis that one function of brain-based rGH might be as a mediator of the short-loop negative feedback system controlling pituitary rGH release. If brain-based rGH were to function as a mediator of such a system, then in situations where serum rGH levels are decreased, brain rGH concentrations should increase, indicating activation of a negative feedback loop. In the present communication we report that significantly decreased serum GH levels in oophorectomized and in thyroidectomized rats were coupled with a significant increase in rGH concentrations in the hypothalamus and in the amygdala. By contrast, adrenalectomy, which was not associated with any changes in levels of GH in serum caused no perturbations in levels of rGH in the brain. These discordant changes in serum and brain-based rGH are findings compatible with the hypothesis that one function of brain-based rGH is as a mediator of the short-loop negative feedback system regulating the release of pituitary GH.

The question of whether ethanol's (ETOH's) known suppressive effect on serum luteinizing hormone (LH) could be mediated directly at the anterior pituitary level was addressed by examining the effects of ETOH in vitro on release of LH from cultured male rat pituitary cells. The impact of added ethanol concentrations ranging from 50 to 400 mg% on LH release was examined in the basal state and after stimulation by gonadotropin-releasing hormone (GnRH) at a dose of 5 x 10(-10) M. While ETOH did not significantly suppress basal LH release, secretion stimulated with GnRH was noted to be attenuated with higher doses of ETOH (greater than or equal to 100 mg%) compared to stimulated control cells. It is concluded that ETOH exposure in vitro alters stimulated LH secretion by acting directly on pituitary gonadotropes.

Ultracentrifugation and sucrose gradient separation techniques have been applied to study of the subcellular distribution of hypothalamic luteinizing hormone (LH). Subcellular particle-bound LH accounted for 42% of the total LH while cytoplasm contained 58% of the total immunoassayable LH in these extracts. 70% of particle-bound LH was present in the P2 fraction and most of the particle-associated LH was found in subfractions of P2 rich in synaptosomes but poor in myelin and mitochondria. While actual amounts of LH in the P3 and P4, the microsomal fractions, were relatively small, the concentration of LH, expressed as nanograms per milligram of protein was quite high. Both content and concentration of LH in the nuclear pellet, P1, were substantially lower. These findings provide further framework for speculation on the role of brain-based LH.

While an attempt was being made to identify the source of the growth hormone releasing factor present in cerebral spinal fluid of man, it was discovered that cells of the rat amygdaloid nucleus, grown in tissue culture, produce a material that is immunologically and chromatographically identical to growth hormone found in the pituitary. Immunoperoxidase staining revealed dense accumulation of the peroxidase-antibody to growth hormone complex in amygdala cells. Significant amounts of growth hormone and adrenocorticotropin could be extracted from this limbic structure. Extracts containing immunoequivalent amounts of growth hormone were measured by bioassay in hypophysectomized rats. Stimulation of the growth of epiphyseal cartilage by extracts of the amygdala was comparable to the stimulation by extracts of anterior pituitary glands. The stimulatory effect of amygdala extracts on adrenal and gonadal size and weight and on growth of thyroid follicular epithelium was also comparable to that of pituitary extracts.

Alphaxalone is considered the anaesthetic of choice in neuroendocrine reproductive studies in female rats, since it appears to have little, if any, effect on release of gonadotrophin-releasing hormone. There has been less study of the effects of this anaesthetic on the male reproductive neuroendocrine axis, however. Accordingly, the time-dependent effects of alphaxalone, as well as of urethane and ketamine, on the increased levels of LH in castrated rats were determined. Each anaesthetic was administered i.p. and each depressed LH levels significantly compared with those in castrated unanaesthetized rats killed by decapitation (controls). The effect of the anaesthetics was noted 15 min after administration and persisted at 30 and 60 min in animals anaesthetized with alphaxalone and urethane. Only in ketamine-anaesthetized animals did serum concentrations of LH finally rise to concentrations not significantly different from those in control rats. Thus alphaxalone, though useful in female neuroendocrine studies, is as profoundly disruptive as other anaesthetics on the male rat hypothalamic-pituitary reproductive unit.

In order to study the impact of short-term ethanol feeding on pituitary luteinizing hormone (LH) levels, LH release and hormone microheterogeneity, 28 female oophorectomized rats were fed either a diet containing 36% ethanol or an isocaloric diet without ethanol for 16 days. On the 14th day of the experiment, all rats were given 50 micrograms of estradiol subcutaneously to provide a uniform steroid milieu and to induce an LH surge, and sacrificed 48 hours later. Total levels of pituitary and serum immunoreactive LH were identical between the ethanol and control groups. However, when pituitary LH was analyzed by isoelectric focusing on agarose gel a distinct difference was found. Four distinct immunoreactive peaks at pI's 3.50-4.55, 5.20-6.50, 7.00-7.50, 8.15-9.30 were noted. Ethanol-treated animals exhibited an 8-fold increase in the acidic LH subspecies in the pI range 3.50-4.55 and similarly more LH was determined at pI 7.00-7.50 compared to controls (P less than 0.01). More LH was found at the basic pI's from control pituitaries, compared to LH from the ethanol-exposed animals (P less than 0.01). In summary, short-term ethanol feeding in the female rats does not cause quantitative changes in pituitary LH levels or in the estrogen-induced LH surge. However, qualitative changes are present in isoelectric focusing patterns. A significant shift to the more acidic species of the pituitary LH isohormone was noted for ethanol-fed animals as compared to controls. These qualitative changes in the LH molecule, seen before quantitative changes could be appreciated, may help to explain why excessive exposure to alcohol results in reproductive impairments both in rats and in humans.